Fumigation techniques are known to improve the power output and boost of an engine. In some situations, fumigation also increases the life of the engine, reduces fuel consumption, and decreases the noise produced by the engine.
In diesel engine fumigation systems, supplemental fuel that has been vaporized is placed into the intake stream of the engine. Specifically, a fuel vaporizer converts liquid fuel into a gas and another device, for instance, a venturi mixer, pulls the vaporized fuel into the main air intake of the engine for use by the engine. The fumigation process provides only a portion of the fuel used by the engine. The remainder of the fuel used by the engine may also be applied to the cylinders of the engine in the conventional manner.
Fumigation systems use various types of fuel as the supplementary fuel that is to be added to the engine. For instance, the supplementary fuel may be of the same type as the primary fuel. However, in many instances, the supplementary fuel is of a different form, for instance, in the form of liquid propane gas (LPG).
Previous fumigation systems add the supplementary fuel to the engine in either a proportional amount to engine boost or at a single preset fuel level. Consequently, previous systems are unable to take into account changes in engine in operating conditions. No feedback from the engine is provided so that the current conditions of the engine can not be used to alter the amount of supplementary fuel added or the timing of when this fuel is added. Because of these draw-backs, previous systems suffer from situations where the engine becomes over-boosted and over-revved. The over-boosting and over-revving of the engine results in wasted fuel and the decreased performance and life of the engine.
Additionally, in previous systems, regulators were activated by the reduced pressure signal (with respect to ambient pressure) that is developed in the signal generator device installed into the engine intake air stream. Fuel flow is completely reactionary, based on the difference of the signal generator pressure to the ambient pressure.
Moreover, in some previous systems, the flow of a liquid or gas through a restriction is based on the difference of pressure from one side of the restriction to the other. As the pressure difference increases, so does the volume of flow. Unfortunately, the difference may be from increased upstream pressure, or decreased downstream pressure, which is subject to vehicle conditions and out control of the fumigation system. As the flow increases, the flow crosses into the “critical” or supersonic zone. When this situation occurs, the volume of the flow (in cubic feet per minute) does not increase with additional pressure difference across the restriction, so a change in downstream pressure will not affect flow.